1. Field of the Invention
This invention relates to masks for semiconductor manufacturing and more particularly to phase-shifting masks.
2. Description of Related Art
This invention teaches an electronically controlled universal phase-shift mask in a stepper exposure system. The pixel dynamic mask e.g., a SLM (Spatial Light Modulator) can be controlled to have phase-shift features.
Pfauler et al. xe2x80x9cHigh-Throughput Optical Direct Write Lithographyxe2x80x9d, Solid State Technology (June 1997), pp. 175-176, 178, 180, 182 describes a direct write lithography system using a programmable phase-modulated spatial light modulator (SLM) system in which the image is reflected from the SLM onto a semiconductor wafer. The spatial light modulator comprises an array of rectangular electrodes with a reflective, deformable viscoelastic layer on top. The SLM serves as a plane mirror in an optical system.
U.S. Pat. No. 5,641,937 of Nelson for xe2x80x9cMethod for High Resolution Printingxe2x80x9d shows an SLM in a printing system.
U.S. Pat. No. 5,600,485 of Iwaki et al. for xe2x80x9cOptical Pattern Recognition System and Method of Ferroelectric Liquid Crystal Spatial Light Modulatorxe2x80x9d shows a pattern recognition system using a SLM (spatial light modulator).
U.S. Pat. No. 5,724,447 of Fukushima for xe2x80x9cOptical Transform System for Three-Dimensional Object Recognitionxe2x80x9d shows an image detection system for phase-shift masks using an SLM and a CCD.
Levenson et al xe2x80x9cImproving Resolution in Photolithography with a Phase-Shifting Maskxe2x80x9d, IEEE Transactions on Electron Devices, VOL. ED-29. No. 12, (Dec. 1982), pp. 1828-1836.
Levenson xe2x80x9cPhase-Shifting Mask Strategies: Isolated Dark Linesxe2x80x9d, Microlithograpy World, (March/April 1992) pp. 6-12).
A problem with the prior art is that it is necessary to prepare entire sets of various layer masks for a single device. With a conventional binary mask the resolution is limited at the near exposure wavelength which is a disadvantage.
In accordance with a first aspect of this invention, a dynamic mask exposure system and method employs a support for a workpiece, a source of a beam of exposure radiation, a transmissive dynamic mask with matrices of actuator lines arranged orthogonally and binary pixel units which are opaque or transparent as a function of control inputs to the actuator lines, the transmissive dynamic mask has a top surface and a bottom surface. A control system is connected to supply pixel control signals to the actuator lines of the transmissive dynamic phase-shifting mask to form a pattern of transparent regions and opaque regions. The beam is directed down onto the top surface of the mask. The beam which passes through the transparent regions projects a pattern from the mask onto the support where the workpiece is to be located. Preferably the control system comprises a computer and a direct access storage device for storing patterning data; the transmissive dynamic mask comprises a transmissive spatial light modulator; the source of the beam of exposure radiation comprises a collimated light beam, preferably provided by at least one condenser lens projecting the collimated light beam onto the top surface of the mask. A projection lens system projects and focuses the pattern from the mask onto the support from the bottom surface of the mask.
In accordance with another aspect of this invention, a dynamic mask exposure system and method employs a support for a workpiece and a source of a beam of exposure radiation. A transmissive dynamic phase-shifting mask with orthogonally arranged matrices of actuator lines and binary pixel units which are opaque or transparent as a function of control inputs to the actuator lines, the transmissive dynamic mask having a top surface and a bottom surface is employed. A control system is connected to supply pixel control signals to the actuator lines of the transmissive dynamic mask to form a pattern of transparent regions and opaque regions. The beam is directed down onto the top surface of the mask. An image detection element for detecting a pattern of radiation projected thereon is located on the top surface of the support. The beam passes through the transparent regions and projects a pattern from the mask onto the support where the image detection element is to be located. Means for providing signals represent the pattern to the control system. The source of the beam of exposure radiation comprises a collimated light beam provided by at least one condenser lens projecting the collimated light beam onto the top surface of the mask. Preferably the control system comprises a computer and a direct access storage device for storing patterning data; the transmissive dynamic mask comprises a transmissive spatial light modulator; and a projection lens system projects and focuses the pattern from the mask onto the support from the bottom surface of the mask.